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To get the list of all values of certain fields in MongoDB, you can use distinct(). The syntax is as follows −db.yourCollectionName.distinct( "yourFieldName");To understand the above syntax, let us create a collection with the document. The query to create a collection with a document is as follows −> db.listAllValuesOfCeratinFieldsDemo.insertOne({"ListOfValues":[10, 20, 30]}); { "acknowledged" : true, "insertedId" : ObjectId("5c8fc89ed3c9d04998abf011") } > db.listAllValuesOfCeratinFieldsDemo.insertOne({"ListOfValues":[40, 50, 60]}); { "acknowledged" : true, "insertedId" : ObjectId("5c8fc8abd3c9d04998abf012") } > db.listAllValuesOfCeratinFieldsDemo.insertOne({"ListOfValues":[10, 20, 30]}); { "acknowledged" : true, "insertedId" : ObjectId("5c8fc8d7d3c9d04998abf013") } > db.listAllValuesOfCeratinFieldsDemo.insertOne({"ListOfValues":[40, 50, 70]}); { "acknowledged" : true, "insertedId" ... Read More
You can change the datatype of a column in a table using the ALTER TABLE command.SyntaxALTER TABLE Sales MODIFY COLUMN column_name column_new_datatuypeAssume we have a table named Sales in the database with 7 columns namely ProductName, CustomerName, DispatchDate, DeliveryTime, Price, Location and, ID with description as:+--------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------+--------------+------+-----+---------+-------+ | ProductName | varchar(255) | YES | | NULL | | | CustomerName | varchar(255) | YES | | NULL ... Read More
In this section we will see what is the RTTI (Runtime Type Information) in C++. In C++ the RTTI is a mechanism, that exposes information about an object’s datatype during runtime. This feature can be available only when the class has at least one virtual function. It allows the type of an object to be determined when the program is executing.In the following example the first code will not work. It will generate an error like “cannot dynamic_cast base_ptr (of type Base*) to type ‘class Derived*’ (Source type is not polymorphic)”. This error comes because there is no virtual function ... Read More
This example demonstrates how can I make my custom objects ParcelableStep 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. In the above code, we have taken button view to show parcel object values.Step 3 − Add the following code to src/MainActivity.javapackage com.example.myapplication; import android.os.Build; import android.os.Bundle; import android.support.annotation.RequiresApi; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.widget.Toast; public class MainActivity extends AppCompatActivity { parcleObject sample; @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP) @Override protected ... Read More
To check any services related to location in ios with swift we can use the CLLocationManager.In this example we’ll see how to check if the location manager is running or not. We’ll do this with help of an sample project. So, create a new project. First we need to create a locationManager object, so in your view controller.var locationManager = CLLocationManager()Now, we first of all we need to check if the location services are enabled on the device or not. To check this we’ll useCLLocationManager.locationServicesEnabled() function, which returns a Boolean value showing whether the location service on device is active ... Read More
You can use $all operator. Let us first create a collection with documents −> db.subsetOfAnArrayDemo.insertOne({"StudentProgrammingSkills": ["Java", "MongoDB", "MySQL", "C++", "Data Structure", "Algorithm", "Python", "Oracle", "SQL Server"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cb9d1e1895c4fd159f80804") }Following is the query to display all documents from the collection with the help of find() method −> db.subsetOfAnArrayDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cb9d1e1895c4fd159f80804"), "StudentProgrammingSkills" : [ "Java", "MongoDB", "MySQL", "C++", "Data Structure", "Algorithm", "Python", ... Read More
To insert a special character such as “ ‘ “ (single quote) into MySQL, you need to use \’ escape character. The syntax is as follows −insert into yourTableName(yourColumnName) values(' yourValue\’s ');To understand the above syntax, let us create two tables. The query to create first table is as follows −mysql> create table AvoidInsertErrorDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Sentence text -> ); Query OK, 0 rows affected (0.53 sec)Now you can insert special character such as ‘ in the table using insert command. The query is as follows −mysql> insert into AvoidInsertErrorDemo(Sentence) values('a ... Read More
Search a value in a Pair Class using the contains() method.Let us first see what we need to work with JavaTuples. To work with Pair class in JavaTuples, you need to import the following package −import org.javatuples.Pair;Note − Steps to download and run JavaTuples program If you are using Eclipse IDE to run Pair Class in JavaTuples, then Right Click Project → Properties → Java Build Path → Add External Jars and upload the downloaded JavaTuples jar file.The following is an example −Exampleimport org.javatuples.Pair; public class Demo { public static void main(String[] args) { Pair < ... Read More
Let’s say you have a table with UserLoginTime column wherein we have stored some values for sample. This is the login time of users and we want to filter all these records on the basis of current day, month and year i.e. the current date. We will beLet us now create the table we discussed abovemysql> create table userLoginInformation - > ( - > UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, - > UserName varchar(20), - > UserLoginTime datetime - > ); Query OK, 0 rows affected (0.79 sec)Insert some records in the table using ... Read More
A hit counter tells you about the number of visits on a particular page of your web site. Usually, you attach a hit counter with your index.jsp page assuming people first land on your home page.To implement a hit counter you can make use of the Application Implicit object and associated methods getAttribute() and setAttribute().This object is a representation of the JSP page through its entire lifecycle. This object is created when the JSP page is initialized and will be removed when the JSP page is removed by the jspDestroy() method.Following is the syntax to set a variable at the ... Read More